1. Field of the Invention
In general the present invention relates to interconnect structures. Specifically, the present invention relates to an interconnect structure having a grain growth promotion layer on top of a Cu plating seed layer.
2. Related Art
With continual shrinking of interconnect structures, an advanced copper (Cu) metallization process is required to maintain/optimize a final Cu microstructure. In a traditional approach, the Cu plating process is performed directly on top of a Cu seeding layer. After that, a high temperature annealing process is carried out for Cu grain growth. However, it has been observed that the grain growth rate is faster in the plated Cu than in the seeding layer, which then results in small grains at the bottom of the interconnect features.
A demonstration of an existing approach is shown in FIG. 1. Specifically, as shown, an interconnect structure 10 is formed by forming a Cu seeding layer 12 directly on a diffusion barrier layer 14. However, as mentioned above, with the continual shrinkage of these structures, grain growth rates need to improve. In view of the foregoing, there exists a need for an interconnect structure and method for forming the same that addresses these issues.